As for probiotics and yeast, I have no doubt that she has some sort of yeast overgrowth. Can yeast also cause UC?
Yes, there can be a fungal link with UC. Yeast/Candida is not the only fungus implicated. There are over 400 kinds known to cause disease.
If you noticed a worsening of symptoms after Christmas by letting her eat what she wanted, I'm thinking that is a clue that choice of food (high carbs feed fungus) is a player in this, as well. I know for me I may feel "off" from Halloween through the New Year with all the extra junk I put in my mouth. It's tough to supervise her every bite, but maybe just don't keep the "blatant" sugar sources around for her to be tempted...you know, chips, candy,
cookies, ice cream, etc.
One reason probiotics can help is because they make organic acids that not only prevent the growth of fungi such as yeasts, but also neutralize mycotoxins in the intestines before they make it to the bloodstream. Why did your transplant doctor request she stop taking them?...just wondering.